Solid Electrolytic Capacitor with Enhanced Mechanical Stability Under Extreme Conditions

ABSTRACT

Described is a capacitor assembly that is thermally and mechanically stable under extreme conditions. Thermal stability is provided by enclosing and hermetically sealing the capacitor element within a housing in the presence of a gaseous atmosphere that contains an inert gas, thereby limiting the amount of oxygen and moisture supplied to the solid electrolyte of the capacitor. To provide good mechanical stability, the assembly contains at least one external termination (e.g., anode and/or cathode termination) extending beyond an outer periphery of a surface of the housing. The degree to which the external termination extends beyond the outer periphery relative to the dimension of the housing is selectively controlled to increase the surface area available for soldering to a circuit board.

RELATED APPLICATIONS

The present application claims priority to U.S. Provisional ApplicationSer. Nos. 61/622,651, filed on Apr. 11, 2012 and 61,659,529, filed onJun. 14, 2012, which are incorporated herein in their entirety byreference thereto.

BACKGROUND OF THE INVENTION

Electrolytic capacitors (e.g., tantalum capacitors) are increasinglybeing used in the design of circuits due to their volumetric efficiency,reliability, and process compatibility. For example, one type ofcapacitor that has been developed is a solid electrolytic capacitor thatincludes an anode (e.g., tantalum), a dielectric oxide film (e.g.,tantalum pentoxide, Ta₂O₅) formed on the anode, a solid electrolytelayer, and a cathode. The solid electrolyte layer may be formed from aconductive polymer, such as described in U.S. Pat. Nos. 5,457,862 toSakata, et al., 5,473,503 to Sakata, et al., 5,729,428 to Sakata, etal., and 5,812,367 to Kudoh, et al. Unfortunately, however, thestability of such solid electrolytes is poor at high temperatures due tothe tendency to transform from a doped to an un-doped state, or viceversa. In response to these and other problems, capacitors have beendeveloped that are hermetically sealed to limit the contact of oxygenwith the conductive polymer during use. U.S. Patent Publication No.2009/0244812 to Rawal, et al., for instance, describes a capacitorassembly that includes a conductive polymer capacitor that is enclosedand hermetically sealed within a ceramic housing in the presence of aninert gas. According to Rawal, et al., the ceramic housing limits theamount of oxygen and moisture supplied to the conductive polymer so thatit is less likely to oxidize in high temperature environments, thusincreasing the thermal stability of the capacitor assembly. Despite thebenefits achieved, however, problems nevertheless remain. For example,the capacitor can sometimes become mechanically instable under extremeconditions (e.g., high temperature of above about 175° C. and/or highvoltage of above about 35 volts), leading to delamination from thecircuit board and poor electrical performance.

As such, a need currently exists for a solid electrolytic capacitorassembly having improved performance under extreme conditions.

SUMMARY OF THE INVENTION

In accordance with one embodiment of the present invention, a capacitorassembly is disclosed that comprises a capacitor element comprising ananode formed from an anodically oxidized, sintered porous body and asolid electrolyte coating the anode. The assembly also comprises ahousing that defines an interior cavity within which the capacitorelement is positioned and hermetically sealed. The housing contains asurface having a dimension in a longitudinal direction and a dimensionin a transverse direction, the surface further defining an outerperiphery. An anode termination is in electrical connection with theanode body, the anode termination containing an external anodetermination portion that is located adjacent to the surface of thehousing. A cathode termination is in electrical connection with thesolid electrolyte, the cathode termination containing an externalcathode termination portion that is located adjacent to the surface ofthe housing. The external anode termination portion, the externalcathode termination portion, or both extend outwardly beyond the outerperiphery of the housing surface in the transverse direction by acertain distance.

In accordance with another embodiment of the present invention, acapacitor assembly is disclosed that comprises a capacitor elementcomprising an anode formed from an anodically oxidized, sintered porousbody and a solid electrolyte coating the anode. The assembly alsocomprises a housing that defines an interior cavity within which thecapacitor element is positioned and hermetically sealed in the presenceof a gaseous atmosphere that contains an inert gas. The housing containsa lower surface having a dimension in a longitudinal direction and adimension in a transverse direction, the lower surface further definingan outer periphery. An anode termination is in electrical connectionwith the anode body, the anode termination containing an external anodetermination portion that is located adjacent and provided in a planegenerally parallel to the lower surface of the housing. The externalanode termination portion extends outwardly beyond the outer peripheryof the housing surface in the transverse direction by a first distance.A cathode termination is in electrical connection with the solidelectrolyte, the cathode termination containing an external cathodetermination portion that is located adjacent and provided in a planegenerally parallel to the lower surface of the housing. The externalcathode termination portion extends outwardly beyond the outer peripheryof the housing surface in the transverse direction by a second distance.

In accordance with still another embodiment of the present invention, acapacitor assembly is disclosed that comprises a capacitor elementcomprising an anode formed from an anodically oxidized, sintered porousbody and a solid electrolyte coating the anode. The assembly alsocomprises a housing that defines an interior cavity within which thecapacitor element is positioned and hermetically sealed. The housingcontains a surface having a dimension in a longitudinal direction and adimension in a transverse direction, the surface further defining anouter periphery. An anode termination is in electrical connection withthe anode body, the anode termination containing an external anodetermination portion that is located adjacent to the surface of thehousing. A cathode termination is in electrical connection with thesolid electrolyte, the cathode termination containing an externalcathode termination portion that is located adjacent to the surface ofthe housing. The external anode termination portion, the externalcathode termination portion, or both have at least one side that extendsoutwardly beyond the outer periphery of the housing surface in thetransverse direction by a certain distance. The side of the externalanode termination portion, the side of the external cathode terminationportion, or both sides are folded at the outer periphery so that thesides are adjacent to a wall of the housing and perpendicular to thehousing surface.

Other features and aspects of the present invention are set forth ingreater detail below.

BRIEF DESCRIPTION OF THE DRAWINGS

A full and enabling disclosure of the present invention, including thebest mode thereof, directed to one of ordinary skill in the art, is setforth more particularly in the remainder of the specification, whichmakes reference to the appended figures in which:

FIG. 1 is a cross-sectional side view of one embodiment of the capacitorassembly of the present invention;

FIG. 2 is a bottom view of the capacitor assembly of FIG. 1;

FIG. 3 is a cross-sectional side view of another embodiment of thecapacitor assembly of the present invention;

FIG. 4 is a top view of yet another embodiment of the capacitor assemblyof the present invention;

FIG. 5 is a bottom view of another embodiment of the capacitor assemblyof the present invention;

FIG. 6 is a bottom view of still another embodiment of the capacitorassembly of the present invention;

FIG. 7( a) is a cross-sectional side view of another embodiment of thecapacitor assembly of the present invention;

FIG. 7( b) is a cross-sectional side view of yet another embodiment ofthe capacitor assembly of the present invention;

FIG. 8( a) is a bottom view of the capacitor assembly of FIG. 7( a);

FIG. 8( b) is a bottom view of the capacitor assembly of FIG. 7( b);

FIG. 9( a) is a bottom view of another embodiment of the capacitorassembly of the present invention; and

FIG. 9( b) is a bottom view of still another embodiment of the capacitorassembly of the present invention.

Repeat use of references characters in the present specification anddrawings is intended to represent same or analogous features or elementsof the invention.

DETAILED DESCRIPTION OF REPRESENTATIVE EMBODIMENTS

It is to be understood by one of ordinary skill in the art that thepresent discussion is a description of exemplary embodiments only, andis not intended as limiting the broader aspects of the presentinvention, which broader aspects are embodied in the exemplaryconstruction.

Generally speaking, the present invention is directed to a capacitorassembly that is thermally and mechanically stable under extremeconditions. Thermal stability is provided by enclosing and hermeticallysealing the capacitor element within a housing in the presence of agaseous atmosphere that contains an inert gas, thereby limiting theamount of oxygen and moisture supplied to the solid electrolyte of thecapacitor. To provide good mechanical stability, the capacitor assemblyalso contains at least one external termination (e.g., anode and/orcathode termination) that extends beyond an outer periphery of a surfaceof the housing. The degree to which the external termination extendsbeyond the outer periphery relative to the dimension of the housing isselectively controlled in the present invention to increase the degreeof surface area available for soldering to a circuit board. It isbelieved that this can help the capacitor assembly to better withstandvibrational forces incurred during use without delaminating from thecircuit board. In this manner, the capacitor assembly is able to betterfunction in extreme conditions. One particular benefit of the presentinvention is that the likelihood of delamination can be reduced withoutsubstantially increasing the surface area that the assembly occupies onthe board. This is because the improved mechanical stability isaccomplished by selectively controlling the size of the externaltermination rather than increasing the size of the housing and/orcapacitor element.

Various embodiments of the present invention will now be described inmore detail.

I. Capacitor Element

A. Anode

When the capacitor assembly is used in high voltage applications, it isoften desired that the anode of the capacitor element is formed from apowder having a relatively low specific charge, such as less than about70,000 microFarads*Volts per gram (“μF*V/g”), in some embodiments about2,000 μF*V/g to about 65,000 μF*V/g, and in some embodiments, from about5,000 to about 50,000 μF*V/g. Of course, although powders of a lowspecific charge may sometimes be desired, it is by no means arequirement. Namely, the powder may also have a relatively high specificcharge of about 70,000 microFarads*Volts per gram (“μF*V/g”) or more, insome embodiments about 80,000 μF*V/g or more, in some embodiments about90,000 μF*V/g or more, in some embodiments about 100,000 μF*V/g or more,and in some embodiments, from about 120,000 to about 250,000 μF*V/g.

The powder may contain a valve metal (i.e., metal that is capable ofoxidation) or valve metal-based compound, such as tantalum, niobium,aluminum, hafnium, titanium, alloys thereof, oxides thereof, nitridesthereof, and so forth. For example, the valve metal composition maycontain an electrically conductive oxide of niobium, such as niobiumoxide having an atomic ratio of niobium to oxygen of 1:1.0±1.0, in someembodiments 1:1.0±0.3, in some embodiments 1:1.0±0.1, and in someembodiments, 1:1.0±0.05. For example, the niobium oxide may beNbO_(0.7), NbO_(1.0), NbO_(1.1), and NbO₂. Examples of such valve metaloxides are described in U.S. Pat. Nos. 6,322,912 to Fife; 6,391,275 toFife et al.; 6,416,730 to Fife et al.; 6,527,937 to Fife; 6,576,099 toKimmel, et al.; 6,592,740 to Fife, et al.; and 6,639,787 to Kimmel, etal.; and 7,220,397 to Kimmel, et al., as well as U.S. Patent ApplicationPublication Nos. 2005/0019581 to Schnitter; 2005/0103638 to Schnitter,et al.; 2005/0013765 to Thomas, et al.

The particles of the powder may be flaked, angular, nodular, andmixtures or variations thereof. The particles also typically have ascreen size distribution of at least about 60 mesh, in some embodimentsfrom about 60 to about 325 mesh, and in some embodiments, from about 100to about 200 mesh. Further, the specific surface area is from about 0.1to about 10.0 m²/g, in some embodiments from about 0.5 to about 5.0m²/g, and in some embodiments, from about 1.0 to about 2.0 m²/g. Theterm “specific surface area” refers to the surface area determined bythe physical gas adsorption (B.E.T.) method of Bruanauer, Emmet, andTeller, Journal of American Chemical Society, Vol. 60, 1938, p. 309,with nitrogen as the adsorption gas. Likewise, the bulk (or Scott)density is typically from about 0.1 to about 5.0 g/cm³, in someembodiments from about 0.2 to about 4.0 g/cm³, and in some embodiments,from about 0.5 to about 3.0 g/cm³.

Other components may be added to the powder to facilitate theconstruction of the anode body. For example, a binder and/or lubricantmay be employed to ensure that the particles adequately adhere to eachother when pressed to form the anode body. Suitable binders may includecamphor, stearic and other soapy fatty acids, Carbowax (Union Carbide),Glyptal (General Electric), polyvinyl alcohols, naphthalene, vegetablewax, and microwaxes (purified paraffins). The binder may be dissolvedand dispersed in a solvent. Exemplary solvents may include water,alcohols, and so forth. When utilized, the percentage of binders and/orlubricants may vary from about 0.1% to about 8% by weight of the totalmass. It should be understood, however, that binders and lubricants arenot required in the present invention.

The resulting powder may be compacted using any conventional powderpress mold. For example, the press mold may be a single stationcompaction press using a die and one or multiple punches. Alternatively,anvil-type compaction press molds may be used that use only a die andsingle lower punch. Single station compaction press molds are availablein several basic types, such as cam, toggle/knuckle and eccentric/crankpresses with varying capabilities, such as single action, double action,floating die, movable platen, opposed ram, screw, impact, hot pressing,coining or sizing. After compaction, the resulting anode body may thenbe diced into any desired shape, such as square, rectangle, circle,oval, triangle, hexagon, octagon, heptagon, pentagon, etc. The anodebody may also have a “fluted” shape in that it contains one or morefurrows, grooves, depressions, or indentations to increase the surfaceto volume ratio to minimize ESR and extend the frequency response of thecapacitance. The anode body may then be subjected to a heating step inwhich most, if not all, of any binder/lubricant are removed. Forexample, the anode body is typically heated by an oven that operates ata temperature of from about 150° C. to about 500° C. Alternatively, thebinder/lubricant may also be removed by contacting the pellet with anaqueous solution, such as described in U.S. Pat. No. 6,197,252 toBishop, et al.

Once formed, the anode body is then sintered. The temperature,atmosphere, and time of the sintering may depend on a variety offactors, such as the type of anode, the size of the anode, etc.Typically, sintering occurs at a temperature of from about from about800° C. to about 1900° C., in some embodiments from about 1000° C. toabout 1500° C., and in some embodiments, from about 1100° C. to about1400° C., for a time of from about 5 minutes to about 100 minutes, andin some embodiments, from about 30 minutes to about 60 minutes. Ifdesired, sintering may occur in an atmosphere that limits the transferof oxygen atoms to the anode. For example, sintering may occur in areducing atmosphere, such as in a vacuum, inert gas, hydrogen, etc. Thereducing atmosphere may be at a pressure of from about 10 Torr to about2000 Torr, in some embodiments from about 100 Torr to about 1000 Torr,and in some embodiments, from about 100 Torr to about 930 Torr. Mixturesof hydrogen and other gases (e.g., argon or nitrogen) may also beemployed.

An anode lead may also be connected to the anode body that extends in alongitudinal direction therefrom. The anode lead may be in the form of awire, sheet, etc., and may be formed from a valve metal compound, suchas tantalum, niobium, niobium oxide, etc. Connection of the lead may beaccomplished using known techniques, such as by welding the lead to thebody or embedding it within the anode body during formation (e.g., priorto compaction and/or sintering).

The anode is also coated with a dielectric. The dielectric may be formedby anodically oxidizing (“anodizing”) the sintered anode so that adielectric layer is formed over and/or within the anode. For example, atantalum (Ta) anode may be anodized to tantalum pentoxide (Ta₂O₅).Typically, anodization is performed by initially applying a solution tothe anode, such as by dipping anode into the electrolyte. A solvent isgenerally employed, such as water (e.g., deionized water). To enhanceionic conductivity, a compound may be employed that is capable ofdissociating in the solvent to form ions. Examples of such compoundsinclude, for instance, acids, such as described below with respect tothe electrolyte. For example, an acid (e.g., phosphoric acid) mayconstitute from about 0.01 wt. % to about 5 wt. %, in some embodimentsfrom about 0.05 wt. % to about 0.8 wt. %, and in some embodiments, fromabout 0.1 wt. % to about 0.5 wt. % of the anodizing solution. Ifdesired, blends of acids may also be employed.

A current is passed through the anodizing solution to form thedielectric layer. The value of the formation voltage manages thethickness of the dielectric layer. For example, the power supply may beinitially set up at a galvanostatic mode until the required voltage isreached. Thereafter, the power supply may be switched to apotentiostatic mode to ensure that the desired dielectric thickness isformed over the entire surface of the anode. Of course, other knownmethods may also be employed, such as pulse or step potentiostaticmethods. The voltage at which anodic oxidation occurs typically rangesfrom about 4 to about 250 V, and in some embodiments, from about 9 toabout 200 V, and in some embodiments, from about 20 to about 150 V.During oxidation, the anodizing solution can be kept at an elevatedtemperature, such as about 30° C. or more, in some embodiments fromabout 40° C. to about 200° C., and in some embodiments, from about 50°C. to about 100° C. Anodic oxidation can also be done at ambienttemperature or lower. The resulting dielectric layer may be formed on asurface of the anode and within its pores.

B. Solid Electrolyte

The capacitor element also contains a solid electrolyte that functionsas the cathode for the capacitor. A manganese dioxide solid electrolytemay, for instance, be formed by the pyrolytic decomposition of manganousnitrate (Mn(NO₃)₂). Such techniques are described, for instance, in U.S.Pat. No. 4,945,452 to Sturmer, et al. The solid electrolyte may alsocontain one or more conductive polymer layers. The conductive polymer(s)employed in such layers are typically π-conjugated and have electricalconductivity after oxidation or reduction, such as an electricalconductivity of at least about 1 μS cm⁻¹ after oxidation. Examples ofsuch π-conjugated conductive polymers include, for instance,polyheterocycles (e.g., polypyrroles, polythiophenes, polyanilines,etc.), polyacetylenes, poly-p-phenylenes, polyphenolates, and so forth.Particularly suitable conductive polymers are substituted polythiopheneshaving the following general structure:

wherein,

T is O or S;

D is an optionally substituted C₁ to C₅ alkylene radical (e.g.,methylene, ethylene, n-propylene, n-butylene, n-pentylene, etc.);

R₇ is a linear or branched, optionally substituted C₁ to C₁₈ alkylradical (e.g., methyl, ethyl, n- or iso-propyl, n-, iso-, sec- ortert-butyl, n-pentyl, 1-methylbutyl, 2-methylbutyl, 3-methylbutyl,1-ethylpropyl, 1,1-dimethylpropyl, 1,2-dimethylpropyl,2,2-dimethylpropyl, n-hexyl, n-heptyl, n-octyl, 2-ethylhexyl, n-nonyl,n-decyl, n-undecyl, n-dodecyl, n-tridecyl, n-tetradecyl, n-hexadecyl,n-octadecyl, etc.); optionally substituted C₅ to C₁₂ cycloalkyl radical(e.g., cyclopentyl, cyclohexyl, cycloheptyl, cyclooctyl, cyclononylcyclodecyl, etc.); optionally substituted C₆ to C₁₄ aryl radical (e.g.,phenyl, naphthyl, etc.); optionally substituted C₇ to C₁₈ aralkylradical (e.g., benzyl, o-, m-, p-tolyl, 2,3-, 2,4-, 2,5-, 2-6, 3-4-,3,5-xylyl, mesityl, etc.); optionally substituted C₁ to C₄ hydroxyalkylradical, or hydroxyl radical; and

q is an integer from 0 to 8, in some embodiments, from 0 to 2, and inone embodiment, 0; and

n is from 2 to 5,000, in some embodiments from 4 to 2,000, and in someembodiments, from 5 to 1,000. Example of substituents for the radicals“D” or “R₇” include, for instance, alkyl, cycloalkyl, aryl, aralkyl,alkoxy, halogen, ether, thioether, disulphide, sulfoxide, sulfone,sulfonate, amino, aldehyde, keto, carboxylic acid ester, carboxylicacid, carbonate, carboxylate, cyano, alkylsiiane and alkoxysilanegroups, carboxylamide groups, and so forth.

Particularly suitable thiophene polymers are those in which “D” is anoptionally substituted C₂ to C₃ alkylene radical. For instance, thepolymer may be optionally substituted poly(3,4-ethylenedioxythiophene),which has the following general structure:

Methods for forming conductive polymers, such as described above, arewell known in the art. For instance, U.S. Pat. No. 6,987,663 to Merker,et al. describes various techniques for forming substitutedpolythiophenes from a monomeric precursor. The monomeric precursor may,for instance, have the following structure:

wherein,

T, D, R₇, and q are defined above. Particularly suitable thiophenemonomers are those in which “D” is an optionally substituted C₂ to C₃alkylene radical. For instance, optionally substituted3,4-alkylenedioxythiophenes may be employed that have the generalstructure:

wherein, R₇ and q are as defined above. In one particular embodiment,“q” is 0. One commercially suitable example of 3,4-ethylenedioxthiopheneis available from Heraeus Clevios under the designation Cievios™ M.Other suitable monomers are also described in U.S. Pat. No. 5,111,327 toBlohm, et al. and U.S. Pat. No. 6,635,729 to Groenendaal, et al.Derivatives of these monomers may also be employed that are, forexample, dimers or trimers of the above monomers. Higher molecularderivatives, i.e., tetramers, pentamers, etc. of the monomers aresuitable for use in the present invention. The derivatives may be madeup of identical or different monomer units and used in pure form and ina mixture with one another and/or with the monomers. Oxidized or reducedforms of these precursors may also be employed.

The thiophene monomers are chemically polymerized in the presence of anoxidative catalyst. The oxidative catalyst typically includes atransition metal cation, such as iron(III), copper(II), chromium(VI),cerium(IV), manganese(IV), manganese(VII), ruthenium(III) cations, etc.A dopant may also be employed to provide excess charge to the conductivepolymer and stabilize the conductivity of the polymer. The dopanttypically includes an inorganic or organic anion, such as an ion of asulfonic acid. In certain embodiments, the oxidative catalyst employedin the precursor solution has both a catalytic and doping functionalityin that it includes a cation (e.g., transition metal) and anion (e.g.,sulfonic acid). For example, the oxidative catalyst may be a transitionmetal salt that includes iron(III) cations, such as iron(III) halides(e.g., FeCl₃) or iron(III) salts of other inorganic acids, such asFe(ClO₄)₃ or Fe₂(SO₄)₃ and the iron(III) salts of organic acids andinorganic acids comprising organic radicals. Examples of iron (III)salts of inorganic acids with organic radicals include, for instance,iron(III) salts of sulfuric acid monoesters of C₁ to C₂₀ alkanols (e.g.,iron(III) salt of lauryl sulfate). Likewise, examples of iron(III) saltsof organic acids include, for instance, iron(III) salts of C₁ to C₂₀alkane sulfonic acids (e.g., methane, ethane, propane, butane, ordodecane sulfonic acid); iron (ill) salts of aliphatic perfluorosulfonicacids (e.g., trifluoromethane sulfonic acid, perfluorobutane sulfonicacid, or perfluorooctane sulfonic acid); iron (III) salts of aliphaticC₁ to C₂₀ carboxylic acids (e.g., 2-ethylhexylcarboxylic acid); iron(III) salts of aliphatic perfluorocarboxylic acids (e.g.,trifluoroacetic acid or perfluorooctane acid); iron (III) salts ofaromatic sulfonic acids optionally substituted by C₁ to C₂₀ alkyl groups(e.g., benzene sulfonic acid, o-toluene sulfonic acid, p-toluenesulfonic acid, or dodecylbenzene sulfonic acid); iron (III) salts ofcycloalkane sulfonic acids (e.g., camphor sulfonic acid); and so forth.Mixtures of these above-mentioned iron(III) salts may also be used.Iron(III)-p-toluene sulfonate, iron(III)-o-toluene sulfonate, andmixtures thereof, are particularly suitable. One commercially suitableexample of iron(III)-p-toluene sulfonate is available from HeraeusClevios under the designation Clevios™ C.

Various methods may be utilized to form a conductive polymer layer, Inone embodiment, the oxidative catalyst and monomer are applied, eithersequentially or together, such that the polymerization reaction occursin situ on the part. Suitable application techniques may includescreen-printing, dipping, electrophoretic coating, and spraying, may beused to form a conductive polymer coating. As an example, the monomermay initially be mixed with the oxidative catalyst to form a precursorsolution. Once the mixture is formed, it may be applied to the part andthen allowed to polymerize so that the conductive coating is formed onthe surface. Alternatively, the oxidative catalyst and monomer may beapplied sequentially. In one embodiment, for example, the oxidativecatalyst is dissolved in an organic solvent (e.g., butanol) and thenapplied as a dipping solution. The part may then be dried to remove thesolvent therefrom. Thereafter, the part may be dipped into a solutioncontaining the monomer.

Polymerization is typically performed at temperatures of from about −10°C. to about 250° C., and in some embodiments, from about 0° C. to about200° C., depending on the oxidizing agent used and desired reactiontime. Suitable polymerization techniques, such as described above, maybe described in more detail in U.S. Pat. No. 7,515,396 to Biler. Stillother methods for applying such conductive coating(s) may be describedin U.S. Pat. Nos. 5,457,862 to Sakata, et al., 5,473,503 to Sakata, etal., 5,729,428 to Sakata, et al., and 5,812,367 to Kudoh, et al.

In addition to in situ application, a conductive polymer layer may alsobe applied in the form of a dispersion of conductive polymer particles.Although their size may vary, it is typically desired that the particlespossess a small diameter to increase the surface area available foradhering to the anode part. For example, the particles may have anaverage diameter of from about 1 to about 500 nanometers, in someembodiments from about 5 to about 400 nanometers, and in someembodiments, from about 10 to about 300 nanometers. The D₉₀ value of theparticles (particles having a diameter of less than or equal to the D₉₀value constitute 90% of the total volume of all of the solid particles)may be about 15 micrometers or less, in some embodiments about 10micrometers or less, and in some embodiments, from about 1 nanometer toabout 8 micrometers. The diameter of the particles may be determinedusing known techniques, such as by ultracentrifuge, laser diffraction,etc.

The formation of the conductive polymers into a particulate form may beenhanced by using a separate counterion to counteract the positivecharge carried by the substituted polythiophene. In some cases, thepolymer may possess positive and negative charges in the structuralunit, with the positive charge being located on the main chain and thenegative charge optionally on the substituents of the radical “R”, suchas sulfonate or carboxylate groups. The positive charges of the mainchain may be partially or wholly saturated with the optionally presentanionic groups on the radicals “R.” Viewed overall, the polythiophenesmay, in these cases, be cationic, neutral or even anionic. Nevertheless,they are all regarded as cationic polythiophenes as the polythiophenemain chain has a positive charge.

The counterion may be a monomeric or polymeric anion. Polymeric anionscan, for example, be anions of polymeric carboxylic acids (e.g.,polyacrylic acids, polymethacrylic acid, polymaleic acids, etc.);polymeric sulfonic acids (e.g., polystyrene sulfonic acids (“PSS”),polyvinyl sulfonic acids, etc.); and so forth. The acids may also becopolymers, such as copolymers of vinyl carboxylic and vinyl sulfonicacids with other polymerizable monomers, such as acrylic acid esters andstyrene. Likewise, suitable monomeric anions include, for example,anions of C₁ to C₂₀ alkane sulfonic acids (e.g., dodecane sulfonicacid); aliphatic perfluorosulfonic acids (e.g., trifluoromethanesulfonic acid, perfluorobutane sulfonic acid or perfluorooctane sulfonicacid); aliphatic C₁ to C₂₀ carboxylic acids (e.g.,2-ethyl-hexylcarboxylic acid); aliphatic perfluorocarboxylic acids(e.g., trifluoroacetic acid or perfluorooctanoic acid); aromaticsulfonic acids optionally substituted by C₁ to C₂₀ alkyl groups (e.g.,benzene sulfonic acid, o-toluene sulfonic acid, p-toluene sulfonic acidor dodecylbenzene sulfonic acid); cycloalkane sulfonic acids (e.g.,camphor sulfonic acid or tetrafluoroborates, hexafluorophosphates,perchlorates, hexafluoroantimonates, hexafluoroarsenates orhexachloroantimonates); and so forth. Particularly suitablecounteranions are polymeric anions, such as a polymeric carboxylic orsulfonic acid (e.g., polystyrene sulfonic acid (“PSS”)). The molecularweight of such polymeric anions typically ranges from about 1,000 toabout 2,000,000, and in some embodiments, from about 2,000 to about500,000.

When employed, the weight ratio of such counterions to substitutedpolythiophenes in a given layer is typically from about 0.5:1 to about50:1, in some embodiments from about 1:1 to about 30:1, and in someembodiments, from about 2:1 to about 20:1. The weight of the substitutedpolythiophene referred to in the above-referenced weight ratios refersto the weighed-in portion of the monomers used, assuming that a completeconversion occurs during polymerization.

The dispersion may also contain one or more binders to further enhancethe adhesive nature of the polymeric layer and also increase thestability of the particles within the dispersion. The binders may beorganic in nature, such as polyvinyl alcohols, polyvinyl pyrrolidones,polyvinyl chlorides, polyvinyl acetates, polyvinyl butyrates,polyacrylic acid esters, polyacrylic acid amides, polymethacrylic acidesters, polymethacrylic acid amides, polyacrylonitriles, styrene/acrylicacid ester, vinyl acetate/acrylic acid ester and ethylene/vinyl acetatecopolymers, polybutadienes, polyisoprenes, polystyrenes, polyethers,polyesters, polycarbonates, polyurethanes, polyamides, polyimides,polysulfones, melamine formaldehyde resins, epoxide resins, siliconeresins or celluloses. Crosslinking agents may also be employed toenhance the adhesion capacity of the binders. Such crosslinking agentsmay include, for instance, melamine compounds, masked isocyanates orfunctional silanes, such as 3-glycidoxypropyltrialkoxysilane,tetraethoxysilane and tetraethoxysilane hydrolysate or crosslinkablepolymers, such as polyurethanes, polyacrylates or polyolefins, andsubsequent crosslinking. Other components may also be included withinthe dispersion as is known in the art, such as dispersion agents (e.g.,water), surface-active substances, etc.

If desired, one or more of the above-described application steps may berepeated until the desired thickness of the coating is achieved. In someembodiments, only a relatively thin layer of the coating is formed at atime. The total target thickness of the coating may generally varydepending on the desired properties of the capacitor. Typically, theresulting conductive polymer coating has a thickness of from about 0.2micrometers (“μm”) to about 50 μm, in some embodiments from about 0.5 μmto about 20 μm, and in some embodiments, from about 1 μm to about 5 μm.It should be understood that the thickness of the coating is notnecessarily the same at all locations on the part. Nevertheless, theaverage thickness of the coating on the substrate generally falls withinthe ranges noted above.

The conductive polymer layer may optionally be healed. Healing may occurafter each application of a conductive polymer layer or may occur afterthe application of the entire coating. In some embodiments, theconductive polymer can be healed by dipping the part into an electrolytesolution, and thereafter applying a constant voltage to the solutionuntil the current is reduced to a preselected level. If desired, suchhealing can be accomplished in multiple steps. For example, anelectrolyte solution can be a dilute solution of the monomer, thecatalyst, and dopant in an alcohol solvent (e.g., ethanol). The coatingmay also be washed if desired to remove various byproducts, excessreagents, and so forth.

C. Other Components

If desired, the capacitor element may also contain other layers as isknown in the art. For example, a protective coating may optionally beformed between the dielectric and solid electrolyte, such as one made ofa relatively insulative resinous material (natural or synthetic). Someresinous materials that may be utilized in the present inventioninclude, but are not limited to, polyurethane, polystyrene, esters ofunsaturated or saturated fatty acids (e.g., glycerides), and so forth.For instance, suitable esters of fatty acids include, but are notlimited to, esters of lauric acid, myristic acid, palmitic acid, stearicacid, eleostearic acid, oleic acid, linoleic acid, linolenic acid,aleuritic acid, shellolic acid, and so forth. These esters of fattyacids have been found particularly useful when used in relativelycomplex combinations to form a “drying oil”, which allows the resultingfilm to rapidly polymerize into a stable layer. Such drying oils mayinclude mono-, di-, and/or tri-glycerides, which have a glycerolbackbone with one, two, and three, respectively, fatty acyl residuesthat are esterified. For instance, some suitable drying oils that may beused include, but are not limited to, olive oil, linseed oil, castoroil, tung oil, soybean oil, and shellac. These and other protectivecoating materials are described in more detail U.S. Pat. No. 6,674,635to Fife, et al.

If desired, the part may also be applied with a carbon layer (e.g.,graphite) and silver layer, respectively. The silver coating may, forinstance, act as a solderable conductor, contact layer, and/or chargecollector for the capacitor and the carbon coating may limit contact ofthe silver coating with the solid electrolyte. Such coatings may coversome or all of the solid electrolyte.

Generally speaking, the capacitor element is substantially free ofresins (e.g., epoxy resins) that encapsulate the capacitor element asare often employed in conventional solid electrolytic capacitors. Amongother things, the encapsulation of the capacitor element can lead toinstability in extreme environments, i.e., high temperature (e.g., aboveabout 175° C.) and/or high voltage (e.g., above about 35 volts).

II. Housing

As indicated above, the capacitor element is hermetically sealed withina housing. Hermetic sealing typically occurs in the presence of agaseous atmosphere that contains at least one inert gas so as to inhibitoxidation of the solid electrolyte during use. The inert gas mayinclude, for instance, nitrogen, helium, argon, xenon, neon, krypton,radon, and so forth, as well as mixtures thereof. Typically, inert gasesconstitute the majority of the atmosphere within the housing, such asfrom about 50 wt. % to 100 wt. %, in some embodiments from about 75 wt.% to 100 wt. %, and in some embodiments, from about 90 wt. % to about 99wt. % of the atmosphere. If desired, a relatively small amount ofnon-inert gases may also be employed, such as carbon dioxide, oxygen,water vapor, etc. In such cases, however, the non-inert gases typicallyconstitute 15 wt. % or less, in some embodiments 10 wt. % or less, insome embodiments about 5 wt. % or less, in some embodiments about 1 wt.% or less, and in some embodiments, from about 0.01 wt. % to about 1 wt.% of the atmosphere within the housing. For example, the moisturecontent (expressed in terms of relatively humidity) may be about 10% orless, in some embodiments about 5% or less, in some embodiments about 1%or less, and in some embodiments, from about 0.01 to about 5%.

Any of a variety of different materials may be used to form the housing,such as metals, plastics, ceramics, and so forth. In one embodiment, forexample, the housing includes one or more layers of a metal, such astantalum, niobium, aluminum, nickel, hafnium, titanium, copper, silver,steel (e.g., stainless), alloys thereof (e.g., electrically conductiveoxides), composites thereof (e.g., metal coated with electricallyconductive oxide), and so forth. In another embodiment, the housing mayinclude one or more layers of a ceramic material, such as aluminumnitride, aluminum oxide, silicon oxide, magnesium oxide, calcium oxide,glass, etc., as well as combinations thereof.

The housing may have any desired shape, such as cylindrical, D-shaped,rectangular, triangular, prismatic, etc. Referring to FIGS. 1-2, forexample, one embodiment of a capacitor assembly 100 is shown thatcontains a housing 122 and a capacitor element 120. In this particularembodiment, the housing 122 is generally rectangular. Typically, thehousing and the capacitor element have the same or similar shape so thatthe capacitor element can be readily accommodated within the interiorcavity. In the illustrated embodiment, for example, both the capacitorelement 120 and the housing 122 have a generally rectangular shape.

If desired, the capacitor assembly of the present invention may exhibita relatively high volumetric efficiency. To facilitate such highefficiency, the capacitor element typically occupies a substantialportion of the volume of an interior cavity of the housing. For example,the capacitor element may occupy about 30 vol. % or more, in someembodiments about 50 vol. % or more, in some embodiments about 60 vol. %or more, in some embodiments about 70 vol. % or more, in someembodiments from about 80 vol. % to about 98 vol. %, and in someembodiments, from about 85 vol. % to 97 vol. % of the interior cavity ofthe housing. To this end, the difference between the dimensions of thecapacitor element and those of the interior cavity defined by thehousing are typically relatively small.

In FIG. 1, for example, the capacitor element 120 is shown as having alength (excluding the length of the anode lead 6) that is relativelysimilar to the length of an interior cavity 126 defined by the housing122. For example, the ratio of the length of the anode (in the −ydirection) to the length of the interior cavity ranges from about 0.40to 1.00, in some embodiments from about 0.50 to about 0.99, in someembodiments from about 0.60 to about 0.99, and in some embodiments, fromabout 0.70 to about 0.98. The capacitor element 120 may have a length offrom about 5 to about 10 millimeters, and the interior cavity 126 mayhave a length of from about 6 to about 15 millimeters. Similarly, theratio of the height of the capacitor element 120 (in the −z direction)to the height of the interior cavity 126 may range from about 0.40 to1.00, in some embodiments from about 0.50 to about 0.99, in someembodiments from about 0.60 to about 0.99, and in some embodiments, fromabout 0.70 to about 0.98. The ratio of the width of the capacitorelement 120 (in the −x direction) to the width of the interior cavity126 may also range from about 0.50 to 1.00, in some embodiments fromabout 0.60 to about 0.99, in some embodiments from about 0.70 to about0.99, in some embodiments from about 0.80 to about 0.98, and in someembodiments, from about 0.85 to about 0.95. For example, the width ofthe capacitor element 120 may be from about 2 to about 10 millimetersand the width of the interior cavity 126 may be from about 3 to about 12millimeters, and the height of the capacitor element 120 may be fromabout 0.5 to about 2 millimeters and the height of the interior cavity126 may be from about 0.7 to about 6 millimeters.

Optionally, a polymeric restraint may also be disposed in contact withone or more surfaces of the capacitor element, such as the rear surface,front surface, upper surface, lower surface, side surface(s), or anycombination thereof. The polymeric restraint can reduce the likelihoodof delamination by the capacitor element from the housing. In thisregard, the polymeric restraint may possesses a certain degree ofstrength that allows it to retain the capacitor element in a relativelyfixed positioned even when it is subjected to vibrational forces, yet isnot so strong that it cracks. For example, the restraint may possess atensile strength of from about 1 to about 150 Megapascals (“MPa”), insome embodiments from about 2 to about 100 MPa, in some embodiments fromabout 10 to about 80 MPa, and in some embodiments, from about 20 toabout 70 MPa, measured at a temperature of about 25° C. It is normallydesired that the restraint is not electrically conductive.

Although any of a variety of materials may be employed that have thedesired strength properties noted above, curable thermosetting resinshave been found to be particularly suitable for use in the presentinvention. Examples of such resins include, for instance, epoxy resins,polyimides, melamine resins, urea-formaldehyde resins, polyurethanes,silicone polymers, phenolic resins, etc. In certain embodiments, forexample, the restraint may employ one or more polyorganosiloxanes.Silicon-bonded organic groups used in these polymers may containmonovalent hydrocarbon and/or monovalent halogenated hydrocarbon groups.Such monovalent groups typically have from 1 to about 20 carbon atoms,preferably from 1 to 10 carbon atoms, and are exemplified by, but notlimited to, alkyl (e.g., methyl, ethyl, propyl, pentyl, octyl, undecyl,and octadecyl); cycloalkyl (e.g., cyclohexyl); alkenyl (e.g., vinyl,allyl, butenyl, and hexenyl); aryl (e.g., phenyl, tolyl, xylyl, benzyl,and 2-phenylethyl); and halogenated hydrocarbon groups (e.g.,3,3,3-trifluoropropyl, 3-chloropropyl, and dichlorophenyl). Typically,at least 50%, and more preferably at least 80%, of the organic groupsare methyl. Examples of such methylpolysiloxanes may include, forinstance, polydimethylsiloxane (“PDMS”), polymethylhydrogensiloxane,etc. Still other suitable methyl polysiloxanes may includedimethyldiphenylpolysiloxane, dimethyl/methylphenylpolysiloxane,polymethylphenylsiloxane, methylphenyl/dimethylsiloxane, vinyldimethylterminated polydimethylsiloxane, vinylmethyl/dimethylpolysiloxane,vinyldimethyl terminated vinylmethyl/dimethylpolysiloxane, divinylmethylterminated polydimethylsiloxane, vinylphenylmethyl terminatedpolydimethylsiloxane, dimethylhydro terminated polydimethylsiloxane,methylhydro/dimethylpolysiloxane, methylhydro terminatedmethyloctylpolysiloxane, methylhydro/phenylmethyl polysiloxane, etc.

The organopolysiloxane may also contain one more pendant and/or terminalpolar functional groups, such as hydroxyl, epoxy, carboxyl, amino,alkoxy, methacrylic, or mercapto groups, which impart some degree ofhydrophilicity to the polymer. For example, the organopolysiloxane maycontain at least one hydroxy group, and optionally an average of atleast two silicon-bonded hydroxy groups (silanol groups) per molecule.Examples of such organopolysiloxanes include, for instance,dihydroxypolydimethylsiloxane, hydroxy-trimethylsiloxypolydimethylsiloxane, etc. Other examples of hydroxyl-modifiedorganopolysiloxanes are described in U.S. Patent Application PublicationNo. 2003/0105207 to Kleyer, et al. Alkoxy-modified organopolysiloxanesmay also be employed, such as dimethoxypolydimethylsiloxane,methoxy-trimethylsiloxypolydimethylsiloxane,diethoxypolydimethylsiloxane,ethoxy-trimethylsiloxy-polydimethylsiloxane, etc. Still other suitableorganopolysiloxanes are those modified with at least one aminofunctional group. Examples of such amino-functional polysiloxanesinclude, for instance, diamino-functional polydimethylsiloxanes. Variousother suitable polar functional groups for organopolysiloxanes are alsodescribed in U.S. Patent Application Publication No. 2010/00234517 toPlantenbero, et al.

Epoxy resins are also particularly suitable for use as the polymericrestraint. Examples of suitable epoxy resins include, for instance,glycidyl ether type epoxy resins, such as bisphenol A type epoxy resins,bisphenol F type epoxy resins, phenol novolac type epoxy resins,orthocresol novolac type epoxy resins, brominated epoxy resins andbiphenyl type epoxy resins, cyclic aliphatic epoxy resins, glycidylester type epoxy resins, glycidylamine type epoxy resins, cresol novolactype epoxy resins, naphthalene type epoxy resins, phenol aralkyl typeepoxy resins, cyclopentadiene type epoxy resins, heterocyclic epoxyresins, etc. Still other suitable conductive adhesive resins may also bedescribed in U.S. Patent Application Publication No. 2006/0038304 toOsako, et al. and U.S. Pat. No. 7,554,793 to Chacko.

If desired, curing agents may also be employed in the polymericrestraint to help promote curing. The curing agents typically constitutefrom about 0.1 to about 20 wt. % of the restraint. Exemplary curingagents include, for instance, amines, peroxides, anhydrides, phenolcompounds, silanes, acid anhydride compounds and combinations thereof.Specific examples of suitable curing agents are dicyandiamide, 1-(2cyanoethyl) 2-ethyl-4-methylimidazole, 1-benzyl 2-methylimidazole, ethylcyano propyl imidazole, 2-methylimidazole, 2-phenylimidazole,2-ethyl-4-methylimidazole, 2-undecylimidazole,1-cyanoethyl-2-methylimidazole,2,4-dicyano-6,2-methylimidazolyl-(1)-ethyl-s-triazine, and2,4-dicyano-6,2-undecylimidazolyl-(1)-ethyl-s-triazine, imidazoliumsalts (such as 1-cyanoethyl-2-undecylimidazolium trimellitate,2-methylimidazolium isocyanurate, 2-ethyl-4-methylimidazoliumtetraphenylborate, and 2-ethyl-1,4-dimethylimidazoliumtetraphenylborate, etc. Still other useful curing agents includephosphine compounds, such as tributylphosphine, triphenylphosphine,tris(dimethoxyphenyl)phosphine, tris(hydroxypropyl)phosphine, andtris(cyanoethyl)phsphine; phosphonium salts, such astetraphenylphosphonium-tetraphenylborate,methyltributylphosphonium-tetraphenylborate, andmethyltricyanoethylphosphonium tetraphenylborate); amines, such as2,4,6-tris(dimethylaminomethyl)phenol, benzylmethylamine,tetramethylbutylguanidine, N-methylpiperazine, and2-dimethylamino-1-pyrroline; ammonium salts, such as triethylammoniumtetraphenylborate; diazabicyclo compounds, such as1,5-diazabicyclo[5,4,0]-7-undecene, 1,5-diazabicyclo[4,3,0]-5-nonene,and 1,4-diazabicyclo[2,2,2]-octane; salts of diazabicyclo compounds suchas tetraphenylborate, phenol salt, phenolnovolac salt, and2-ethylhexanoic acid salt; and so forth.

Still other additives may also be employed, such as photoinitiators,viscosity modifiers, suspension aiding agents, pigments, stress reducingagents, coupling agents (e.g., silane coupling agents), nonconductivefillers (e.g., clay, silica, alumina, etc.), stabilizers, etc. Suitablephotoinitiators may include, for instance, benzoin, benzoin methylether, benzoin ethyl ether, benzoin n-propyl ether, benzoin isobutylether, 2,2 dihydroxy-2-phenylacetophenone,2,2-dimethoxy-2-phenylacetophenone 2,2-diethoxy-2-phenylacetophenone,2,2-diethoxyacetophenone, benzophenone, 4,4-bisdialkylaminobenzophenone,4-dimethylaminobenzoic acid, alkyl 4-dimethylaminobenzoate,2-ethylanthraquinone, xanthone, thioxanthone, 2-cholorothioxanthone,etc. When employed, such additives typically constitute from about 0.1to about 20 wt. % of the total composition.

Referring again to FIG. 1, for instance, one embodiment is shown inwhich a single polymeric restraint 197 is disposed in contact with anupper surface 181 and rear surface 177 of the capacitor element 120.While a single restraint is shown in FIG. 1, it should be understoodthat separate restraints may be employed to accomplish the samefunction. In fact, more generally, any number of polymeric restraintsmay be employed to contact any desired surface of the capacitor element.When multiple restraints are employed, they may be in contact with eachother or remain physically separated. For example, in one embodiment, asecond polymeric restraint (not shown) may be employed that contacts theupper surface 181 and front surface 179 of the capacitor element 120.The first polymeric restraint 197 and the second polymeric restraint(not shown) may or may not be in contact with each other. In yet anotherembodiment, a polymeric restraint may also contact a lower surface 183and/or side surface(s) of the capacitor element 120, either inconjunction with or in lieu of other surfaces.

Regardless of how it is applied, it is typically desired that thepolymeric restraint is also in contact with at least one surface of thehousing to help further mechanically stabilize the capacitor element.For example, the restraint may be in contact with an interior surface ofone or more sidewall(s), outer wall, lid, etc. In FIG. 1, for example,the polymeric restraint 197 is in contact with an interior surface 107of sidewall 124 and an interior surface 109 of outer wall 123. While incontact with the housing, it is nevertheless desired that at least aportion of the cavity defined by the housing remains unoccupied to allowfor the inert gas to flow through the cavity and limit contact of thesolid electrolyte with oxygen. For example, at least about 5% of thecavity volume typically remains unoccupied by the capacitor element andpolymer restraint, and in some embodiments, from about 10% to about 50%of the cavity volume.

In certain embodiments, connective members may be employed within theinterior cavity of the housing to facilitate connection to the externalterminations, which are described in more detail below. For example,referring again to FIG. 1, the capacitor assembly 100 may include aconnection member 162 that is formed from a first portion 167 and asecond portion 165. The connection member 162 may be formed fromconductive materials, such as a metal. The first portion 167 and secondportion 165 may be integral or separate pieces that are connectedtogether, either directly or via an additional conductive element (e.g.,metal). In the illustrated embodiment, the second portion 165 isprovided in a plane that is generally parallel to a longitudinaldirection in which the lead 6 extends (e.g., −y direction). The firstportion 167 is “upstanding” in the sense that it is provided in a planethat is generally perpendicular the longitudinal direction in which thelead 6 extends. In this manner, the first portion 167 can limit movementof the lead 6 in the horizontal direction to enhance surface contact andmechanical stability during use. If desired, an insulative material 7(e.g., Teflon™ washer) may be employed around the lead 6.

The first portion 167 may possess a mounting region (not shown) that isconnected to the anode lead 6. The region may have a “U-shape” forfurther enhancing surface contact and mechanical stability of the lead6. Connection of the region to the lead 6 may be accomplished using anyof a variety of known techniques, such as welding, laser welding,conductive adhesives, etc. In one particular embodiment, for example,the region is laser welded to the anode lead 6. Regardless of thetechnique chosen, however, the first portion 167 can hold the anode lead6 in substantial horizontal alignment to further enhance the dimensionalstability of the capacitor assembly 100.

Referring again to FIG. 1, one embodiment of the present invention isshown in which the connective member 162 and capacitor element 120 areconnected to the housing 122 and anode and cathode terminations 127 and129, which are discussed in more detail below. The housing 122 of thisembodiment includes an outer wall 123 and two opposing sidewalls 124between which a cavity 126 is formed that includes the capacitor element120. The outer wall 123 and sidewalls 124 may be formed from one or morelayers of a metal, plastic, or ceramic material such as described above.Although not required, the anode termination 127 may contain an internalportion 127 a that is positioned within the housing 122 and electricallyconnected to the connection member 162 and an external portion 127 bthat is positioned outside of the housing 122 to provide a mountingsurface 201. Likewise, the cathode termination 129 may contain aninternal portion 129 a that is positioned within the housing 122 andelectrically connected to the solid electrolyte of the capacitor element120 and an external portion 129 b that is positioned outside of thehousing 122 to provide a mounting surface 203. It should be understoodthat the entire portion need not be positioned within or external to thehousing. It should also be understood that the internal portion of theterminations can be eliminated if so desired.

In the illustrated embodiment, a conductive trace 127 c extends in theouter wall 123 of the housing to connect the internal portion (firstregion) 127 a and external portion (second region) 127 b. Similarly, aconductive trace 129 c extends in the outer wall 123 of the housing toconnect the internal portion (first region) 127 a and external portion(second region) 127 b. The conductive traces and/or regions of theterminations may be separate or integral. In addition to extendingthrough the outer wall of the housing, the traces may also be positionedat other locations, such as external to the outer wall. Of course, thepresent invention is by no means limited to the use of conductive tracesfor forming the desired terminations. Connection of the externaltermination portions 127 and 129 to the capacitor element 120 maygenerally be made using any known technique, such as welding, laserwelding, conductive adhesives, etc. In one particular embodiment, forexample, a conductive adhesive 131 is used to connect the second portion165 of the connection member 162 to the anode termination 127. Likewise,a conductive adhesive 133 may also be used to connect the cathode of thecapacitor element 120 to the cathode termination 129. The conductiveadhesives may be formed from conductive metal particles contained with aresin composition. The metal particles may be silver, copper, gold,platinum, nickel, zinc, bismuth, etc. The resin composition may includea thermoset resin (e.g., epoxy resin), curing agent (e.g., acidanhydride), and coupling agent (e.g., silane coupling agents). Suitableconductive adhesives are described in U.S. Patent ApplicationPublication No. 2006/0038304 to Osaka, et al.

Once connected in the desired manner, the resulting package ishermetically sealed as described above. Referring again to FIG. 1, forinstance, the housing 122 may also include a lid 125 that is placed onan upper surface of side walls 124 after the capacitor element 120 andthe polymer restraint 197 are positioned within the housing 122. The lid125 may be formed from a ceramic, metal (e.g., iron, copper, nickel,cobalt, etc., as well as alloys thereof), plastic, and so forth. Ifdesired, a sealing member 187 may be disposed between the lid 125 andthe side walls 124 to help provide a good seal. In one embodiment, forexample, the sealing member may include a glass-to-metal seal, Kovar®ring (Goodfellow Camridge, Ltd.), etc. The height of the side walls 124is generally such that the lid 125 does not contact any surface of thecapacitor element 120 so that it is not contaminated. The polymericrestraint 197 may or may not contact the lid 125. When placed in thedesired position, the lid 125 is hermetically sealed to the sidewalls124 using known techniques, such as welding (e.g., resistance welding,laser welding, etc.), soldering, etc. Hermetic sealing generally occursin the presence of inert gases as described above so that the resultingassembly is substantially free of reactive gases, such as oxygen orwater vapor.

It should be understood that the embodiments described are onlyexemplary, and that various other configurations may be employed in thepresent invention for hermetically sealing a capacitor element within ahousing. Referring to FIG. 3, for instance, another embodiment of acapacitor assembly 200 is shown that employs a housing 222 that includesan outer wall 123 and a lid 225 between which a cavity 126 is formedthat includes the capacitor element 120 and optional polymeric restraint197. The lid 225 includes an outer wall 223 that is integral with atleast one sidewall 224. In the illustrated embodiment, for example, twoopposing sidewalls 224 are shown in cross-section. The outer walls 223and 123 both extend in a longitudinal direction (−y direction) and aregenerally parallel with each other and to the longitudinal direction ofthe anode lead 6. The sidewall 224 extends from the outer wall 223 in adirection that is generally perpendicular to the outer wall 123. Adistal end 500 of the lid 225 is defined by the outer wail 223 and aproximal end 501 is defined by a lip 253 of the sidewall 224. The lip253 extends from the sidewall 224 in the longitudinal direction, whichmay be generally parallel to the longitudinal direction of the outerwall 123. The angle between the sidewall 224 and the lip 253 may vary,but is typically from about 60° to about 120°, in some embodiments fromabout 70° to about 110°, and in some embodiments, from about 80° toabout 100° (e.g., about 90°). The lip 253 also defines a peripheral edge251, which may be generally perpendicular to the longitudinal directionin which the lip 253 and outer wall 123 extend. The peripheral edge 251is located beyond the outer periphery of the sidewall 224 and may begenerally coplanar with an edge 151 of the outer wall 123. The lip 253may be sealed to the outer wall 123 using any known technique, such aswelding (e.g., resistance or laser), soldering, glue, etc. For example,in the illustrated embodiment, a sealing member 287 is employed (e.g.,glass-to-metal seal, Kovar® ring, etc.) between the components tofacilitate their attachment. Regardless, the use of a lip describedabove can enable a more stable connection between the components andimprove the seal and mechanical stability of the capacitor assembly.

The embodiments discussed above refer to only a single capacitorelement. It should also be understood, however, that multiple capacitorelements (e.g., 2, 3, etc.) may also be hermetically sealed within ahousing. The multiple capacitor elements may be attached to the housingany of a variety of different techniques. Referring to FIG. 4, forexample one particular embodiment of a capacitor assembly 400 thatcontains two capacitor elements is shown and will now be described inmore detail. More particularly, the capacitor assembly 400 includes afirst capacitor element 420 a in electrical communication with a secondcapacitor element 420 b. In this embodiment, the capacitor elements arealigned so that their major surfaces are in a horizontal configuration.That is, a major surface of the capacitor element 420 a defined by itswidth (−x direction) and length (−y direction) is positioned adjacent toa corresponding major surface of the capacitor element 420 b. Thus, themajor surfaces are generally coplanar. Alternatively, the capacitorelements may be arranged so that their major surfaces are not coplanar,but perpendicular to each other in a certain direction, such as the −zdirection or the −x direction. Of course, the capacitor elements neednot extend in the same direction.

The capacitor elements 420 a and 420 b are positioned within a housing422 that contains an outer wall 423 and sidewalls 424 and 425 thattogether define a cavity 426. Although not shown, a lid may be employedthat covers the upper surfaces of the sidewalls 424 and 425 and sealsthe assembly 400 as described above. A polymeric restraint mayoptionally be employed to help limit the vibration of the capacitorelements. In FIG. 4, for example, separate polymer restraints 497 a and497 b are positioned adjacent to and in contact with the capacitorelements 420 a and 420 b, respectively. The polymer restraints 497 a and497 b may be positioned in a variety of different locations. Further,one of the restraints may be eliminated, or additional restraints may beemployed. In certain embodiments, for example, it may be desired toemploy a polymeric restraint between the capacitor elements to furtherimprove mechanical stability.

Referring again to FIG. 4, for example, the capacitor elements are shownconnected in parallel to a common cathode termination 429. The capacitorassembly 400 also includes connective members 427 and 527 that areconnected to anode leads 406 a and 406 b, respectively, of the capacitorelements 420 a and 420 b. More particularly, the connective member 427contains an upstanding portion 465 and a planar portion 463 that is inconnection with an anode termination (not shown). Likewise, theconnective member 527 contains an upstanding portion 565 and a planarportion 563 that is in connection with an anode termination (not shown).Of course, it should be understood that a wide variety of other types ofconnection mechanisms may also be employed.

III. Terminations

Regardless of the particular configuration of the housing and/orcapacitor element(s), or the manner in which they are connected, theexternal portion of one or more of the terminations (e.g., pads, sheets,plates, frames, etc.) is formed in such a manner that it can reduce thelikelihood of delamination from the circuit board. More particularly,the external portion can extend outwardly beyond the outer perimeter ofa surface of the housing to increase the degree of surface contactbetween the capacitor assembly and the board to which it is mounted. Forexample, in some embodiments, the lower surface of the housing may havean outer periphery defined by its length in the longitudinal direction(e.g., direction in which the anode lead extends) and width in thetransverse direction. In such embodiments, one or more of the externalterminations may extend beyond the periphery of the lower surface of thehousing in the transverse direction. Alternatively or in addition to thetransverse direction, one or more of the external terminations may alsoextend beyond the outer periphery in the longitudinal direction.

Referring again to FIGS. 1-2, for instance, one particular embodiment isshown in which the housing 222 defines a lower surface 171. The lowersurface 171 has an outer periphery 400 defined by its length along the−y axis (e.g., longitudinal direction) and width along the −x axis(e.g., transverse direction). As shown, the external anode terminationportion 127 b and the external cathode termination portion 129 b arelocated adjacent to the lower surface 171 and extend beyond theperiphery 400 along the −x axis. Of course, the particular direction ofextension is not critical, and the portions 127 b and/or 129 b may alsoextend in other various directions beyond the periphery 400, such asalong the −y axis. Further, it should also be understood that anexternal termination portion may also extend from other surfaces of thehousing besides the lower surface, such as the upper surface, rearsurface, etc. Typically, however, at least one of the externaltermination portions is provided in a plane that is generally parallelto the housing surface to which it is adjacent. For example, in theembodiment shown in FIGS. 1-2, the external anode termination portion127 b and the external cathode termination 129 b are provided in a planethat is generally parallel to the lower surface 171 of the housing 222.

As indicated above, the degree to which the external anode terminationportion and/or external cathode termination portion extends beyond theouter periphery of a housing surface is selectively controlled in thepresent invention to achieve a balance between increased stability and areduced circuit board footprint. Referring again to FIG. 2, forinstance, the external anode termination portion 127 b extends a firstdistance “L₁” (e.g., in the −x direction) beyond the periphery 400 andthe external cathode termination portion 129 b extends a second distance“L₂” (e.g., in the −x direction) beyond the periphery 400. The distancesL₁ and L₂ may be the same or different. Typically, the ratio of thedistance L₁ and/or the distance L₂ to the dimension “L₃” of the surface171 of the housing 222 in the same direction (e.g., width in the −xdirection) is typically from about 0.05 to about 3.0, in someembodiments from about 0.1 to about 2.5, and in some embodiments, 0.15to about 2.0. In fact, in certain embodiments, it may be desired thatthe distance L₁ and/or L₂ is even greater than the dimension L₃ so thatthe aforementioned “ratio” is greater than 1. For instance, the distanceL₁ and/or the distance L₂ may be from about 0.25 to about 50millimeters, in some embodiments from about 0.5 to about 40 millimeters,and in some embodiments, from about 1 to about 20 millimeters, while thehousing dimension L₃ may likewise be from about 0.5 to about 40millimeters, in some embodiments from about 2 to about 30 millimeters,and in some embodiments, from about 5 to about 25 millimeters.

In the embodiment shown in FIG. 2, each side of the external anodetermination portion 127 b extends the distance “L₁” beyond the periphery400 and each side of the external cathode termination portion 129 bextends a distance “L₂” beyond the periphery 400. In such cases, thevalues for L₁ and/or L₂ may be the same or different on each side of therespective termination. It should also be understood that only one sideof a termination may extend beyond the periphery if so desired.

The external termination portions 127 b and 129 b may also havedimensions “W₁” and “W₂” (e.g., in the −y direction) that are transverseto the dimensions L₁ and L₂, respectively. The transverse dimensionsmay, for example, range from about 0.1 to about 10 millimeters, in someembodiments from about 0.2 to about 8 millimeters, and in someembodiments, from about 0.5 to about 5 millimeters, while the housingdimension W₃ (e.g., length in the −y direction) may be from about 2 toabout 30 millimeters, in some embodiments from about 3 to about 20millimeters, and in some embodiments, from about 4 to about 15millimeters. The thickness of the terminations may also be selected toenhance stability while still minimizing the thickness of the overallcapacitor assembly. For instance, the thickness may range from about 0.1to about 10 millimeters, in some embodiments from about 0.2 to about 8millimeters, and from about 1 to about 5 millimeters. If desired, thesurface of the terminations may be electroplated with nickel, silver,gold, tin, etc. as is known in the art to ensure that the final part ismountable to the circuit board. In one particular embodiment, thetermination(s) are deposited with nickel and silver flashes,respectively, and the mounting surface is also plated with a tin solderlayer. In another embodiment, the termination(s) are deposited with thinouter metal layers (e.g., gold) onto a base metal layer (e.g., copperalloy) to further increase conductivity.

In the embodiment shown in FIG. 2, the external anode and cathodetermination portions are generally continuous along the entiretransverse dimension (e.g., in the −x direction) of the housing surface171. However, this is not necessarily desired in all embodiments.Referring to FIG. 5, for example, an alternative embodiment isillustrated in which an external anode termination portion 627 extendsbeyond a periphery 700 of a surface 771 of a housing 772 in onedirection (e.g., along the −x axis), while an external cathodetermination portion 629 extends beyond the periphery 700 in the oppositedirection. Thus, in this particular embodiment, the external terminationportions 627 and 629 are discontinuous along the transverse dimension ofthe housing surface. A similar embodiment is also shown in FIG. 6. Inthis particular embodiment, an external anode termination portion 727 isshown that is discontinuous across a surface 871 of a housing 872, butnevertheless extends beyond the periphery 800 in two opposite directions(e.g., along the −x axis). Likewise, a cathode termination 729 is shownthat is discontinuous but extends beyond the periphery 800 in twoopposite directions along the −x axis. This configuration may beparticularly beneficial for those embodiments that employ multiplecapacitor elements, such as shown in FIG. 4 and discussed above.

Further, one or more external terminations may also be folded or bentupwards so that the external termination forms a “J” or “L” shape,resulting in a termination that is adjacent to both the lower surface ofthe capacitor and either an outer wall or sidewall of the capacitordepending on the whether the termination extends beyond the outerperiphery in the transverse direction or the longitudinal direction, asis discussed in more detail below in reference to FIGS. 7( a)-9(b).

Referring now to FIGS. 7( a) through 8(b), for instance, one particularembodiment is shown in which the housing 922 defines a lower surface971. The lower surface 971 has an outer periphery 900 defined by itslength along the −y axis (e.g., longitudinal direction) and width alongthe −x axis (e.g., transverse direction). As shown, the external anodetermination portion 127 b and the external cathode termination portion129 b are located adjacent to the lower surface 971 and extend beyondthe periphery 900 along the −y axis in the longitudinal direction. InFIGS. 7( a) and 8(a), the external termination portions 127 b and 129 bare provided in a plane that is generally parallel to the housingsurface to which they are adjacent. For example, in the embodiment shownin FIG. 7( a), the external anode termination portion 127 b and theexternal cathode termination portion 129 b are provided in a plane thatis generally parallel to the lower surface 971 of the housing 922. InFIGS. 7( b) and 8(b), the external anode termination portion 127 b andexternal cathode termination portion 129 b are also folded or bent sothat the terminations each form a “J” shape or “L” shape against twosurfaces of the housing 922. Thus, at least one side of the anodetermination portion 127 b or cathode termination portion 129 b isperpendicular to the lower surface and adjacent to a sidewall 124 of thehousing 922. For instance, in FIGS. 7( b) and 8(b), the external anodetermination portion 127 b and external cathode termination portion 129 bare both adjacent to the lower surface 971 and sidewall 124 of thehousing 922. It is believed that the “J” or “L”-shaped configurations ofthe external anode and cathode terminations 127 b and 129 b contributesto the mechanical stability to the capacitor assembly under extremeconditions.

As indicated above, the degree to which the external anode terminationportion and/or external cathode termination portion extends beyond theouter periphery of a housing surface is selectively controlled in thepresent invention to achieve a balance between increased stability and areduced circuit board footprint. Referring again to FIG. 7( a), forinstance, the external anode termination portion 127 b extends a firstdistance “L₁” (e.g., in the −y direction) beyond the periphery 900 andthe external cathode termination portion 129 b extends a second distance“L₂” (e.g., in the −y direction) beyond the periphery 900 in thelongitudinal direction. In such cases, the values for L₁ and/or L₂ maybe the same or different on each side of the respective termination. Itshould also be understood that only one side of a termination may extendbeyond the periphery if so desired. Typically, the ratio of the distanceL₁ and/or the distance L₂ to the dimension “L₃” of the surface 971 ofthe housing 922 in the same direction (e.g., length in the −y direction)is typically from about 0.05 to about 2, in some embodiments from about0.10 to about 1.75, and in some embodiments, 0.15 to about 1.5. Incertain embodiments, it may be desired that the distance L₁ and/or L₂ iseven greater than the dimension L₃ so that the aforementioned “ratio” isgreater than 1, while in other embodiments, it may be desired that thedistance L₁ and/or L₂ is less than the dimension L₃ so that theaforementioned “ratio” is less than 1. For instance, the distance L₁and/or the distance L₂ may be from about 0.25 to about 50 millimeters,in some embodiments from about 0.50 to about 40 millimeters, and in someembodiments, from about 1 to about 30 millimeters, while the housingdimension L₃ may be from about M to about 40 millimeters, in someembodiments from about 2 to about 30 millimeters, and in someembodiments, from about 5 to about 25 millimeters.

Further, in FIGS. 7( a) through 8(b), a dimension H is shown thatcorresponds with the height of the sidewall 124 of the housing assembly922 that is perpendicular to lower surface 971. Regardless of the valueof dimension H, it is to be understood that the distances L₁ and/or L₂may be less than, greater than, or equal to the dimension H. Forinstance, the ratio of the distance L₁ and/or L₂ to the dimension H ofsidewall 124 of housing 922 when the external anode and cathodetermination portions are folded onto the sidewall 124 can be from about0.1 to about 2, such as from 0.15 to about 1.5, such as from 0.2 toabout 1.0. Thus, when the external anode and cathode terminationportions 127 b and 129 b are folded or bent so that the portions orsides represented by distances L₁ and L₂ are adjacent to or in contactwith the sidewalls 124 and perpendicular to surface 971, as shown inFIGS. 7( b) and 8(b), the termination portions may extend against thesidewall for a distance that is less than the dimension H of thesidewall 124, as shown in FIG. 7( b), may extend against the sidewallfor a distance that is equal to the dimension H of the sidewall 124, asshown in FIG. 8( b), or may extend beyond the dimension H of sidewall124 (not shown). In any event, the resulting “J” or “L” shapedconfiguration of the external anode and cathode terminations 127 b and129 b due to folding or bending at least one side of the externaltermination portions against the sidewalls 124 of housing 922 enhancesthe mechanical stability of the disclosed capacitor.

Next, as shown in FIG. 8( a), the external termination portions 127 band 129 b may also have dimensions “W₁” and “W₂” (e.g., in the −xdirection) that are transverse to the dimensions L₁ and L₂,respectively. The transverse dimensions may be greater than, equal to,or smaller than the housing dimension, W₃. For example, W₁ and W₂ mayrange from about 0.1 to about 30 millimeters, in some embodiments fromabout 0.2 to about 20 millimeters, and in some embodiments, from about0.5 to about 15 millimeters, while the housing dimension W₃ (e.g.,length in the −x direction) may be from about 2 to about 30 millimeters,in some embodiments from about 3 to about 20 millimeters, and in someembodiments, from about 4 to about 15 millimeters. In the embodimentshown in FIG. 8( a), the external cathode termination portion 129 b isgenerally continuous along the entire transverse dimension (e.g., in the−x direction) of the housing surface 971, while the external anodetermination portion 127 b is not continuous along the entire transversedimension of the surface 971. It is to be understood however, that boththe external anode and cathode termination portions can be generallycontinuous along the entire transverse dimension. It is also to beunderstood that both the external anode and cathode termination portionsmight not be generally continuous along the entire transverse dimension.Regardless of whether the termination portions are continuous along theentire transverse dimension or not, the bending or folding of thetermination portions 127 b and 129 b against the sidewall 124 enhancesthe stability of the capacitor under extreme conditions.

Referring now to FIGS. 9( a) and 9(b), an embodiment of a capacitorassembly similar to that described in FIGS. 2, 5, and 6, is shown,except that in FIG. 9( b), the external anode and cathode terminationportions 127 b and 129 b that extend in a transverse direction (e.g., −xdirection) beyond the periphery 1000 of the capacitor housing 1022 arefolded or bent so that the anode and cathode terminations generally havea “J” shape or “L” shape, where the bent or folded portions or sidesextend against the outer wall 123 of housing 1022 in a direction that isperpendicular to the surface 1071. In this way, the capacitor assemblyis provided with additional mechanical stability under extremeconditions.

Generally, in FIGS. 9( a) and 9(b), a dimension H is shown thatcorresponds with the height of the outer wall 123 of the housingassembly 1022 that is perpendicular to lower surface 1071. Regardless ofthe value of dimension H, it is to be understood that the distances L₁and/or L₂ may be less than, greater than, or equal to the dimension H.For instance, the ratio of the distance L₁ and/or L₂ to the dimension Hof outer wall 123 of housing 1022 when the external anode and cathodetermination portions are folded onto the outer wall 123 can be fromabout 0.1 to about 2, such as from about 0.15 to about 1.5, such as fromabout 0.2 to about 1.0. Thus, when the external anode and cathodetermination portions 127 b and 129 b are folded or bent so that theportions or sides represented by distances L₁ and L₂ are adjacent to orin contact with the outer wall 123 and perpendicular to surface 1071, asshown in FIGS. 9( b) and 9(b), the termination portions may extendagainst the sidewall for a distance that is less than the dimension H ofthe outer wall 123, as shown in FIG. 9( b), may extend against the outerwall for a distance that is equal to the dimension H of the outer wall123, as shown in FIG. 9( b), or may extend beyond the dimension H ofouter wall 123 (not shown). In any event, the resulting “J” or “L”shaped configuration of the external anode and cathode terminations 127b and 129 b due to folding or bending at least one side of the externaltermination portions against the outer walls 123 of housing 1022enhances the mechanical stability of the disclosed capacitor.

As a result of the present invention, the capacitor assembly may exhibitgood stability and excellent electrical properties even when exposed tohigh temperature and high voltage environments. For example, thecapacitor assembly may exhibit a relatively high “breakdown voltage”(voltage at which the capacitor fails), such as about 35 volts or more,in some embodiments about 50 volts or more, in some embodiments about 60volts or more, and in some embodiments, from about 60 volts to about 100volts, such as determined by increasing the applied voltage inincrements of 3 volts until the leakage current reaches 1 mA. Likewise,the capacitor may also be able to withstand relatively high surgecurrents, which is also common in high voltage applications. The peaksurge current may, for example, about 2 times the rated voltage or more,such as range from about 40 Amps or more, in some embodiments about 60Amps or more, and in some embodiments, and in some embodiments, fromabout 120 Amps to about 250 Amps.

The capacitance may likewise be about 1 milliFarad per square centimeter(“mF/cm²”) or more, in some embodiments about 2 mF/cm² or more, in someembodiments from about 5 to about 50 mF/cm², and in some embodiments,from about 8 to about 20 mF/cm². The capacitance may be determined at anoperating frequency of 120 Hz and a temperature of 25° C. In addition,the capacitor assembly can also exhibit a relatively high percentage ofits wet capacitance, which enables it to have only a small capacitanceloss and/or fluctuation in the presence of atmosphere humidity. Thisperformance characteristic is quantified by the “dry to wet capacitancepercentage”, which is determined by the equation:

Dry to Wet Capacitance=(1−([Wet−Dry]/Wet))×100

The capacitor assembly of the present invention, for instance, mayexhibit a dry to wet capacitance percentage of about 80% or more, insome embodiments about 85% or more, in some embodiments about 90% ormore, and in some embodiments, from about 92% to 100%.

The capacitor assembly may also have an equivalence series resistance(“ESR”) of less than about 50 ohms, in some embodiments less than about25 ohms, in some embodiments from about 0.01 to about 10 ohms, and insome embodiments, from about 0.05 to about 5 ohms, measured at anoperating frequency of 100 kHz. In addition, the leakage current, whichgenerally refers to the current flowing from one conductor to anadjacent conductor through an insulator, can be maintained at relativelylow levels. For example, the numerical value of the normalized leakagecurrent of a capacitor of the present invention is, in some embodiments,less than about 1 μA/μF*V, in some embodiments less than about 0.5μA/μF*V, and in some embodiments, less than about 0.1 μA/μF*V, where μAis microamps and uF*V is the product of the capacitance and the ratedvoltage.

The electrical properties, such as described above, may even bemaintained after aging for a substantial amount of time at hightemperatures. For example, the values may be maintained for about 100hours or more, in some embodiments from about 300 hours to about 3000hours, and in some embodiments, from about 400 hours to about 2500 hours(e.g., 500 hours, 600 hours, 700 hours, 800 hours, 900 hours, 1000hours, 1100 hours, 1200 hours, or 2000 hours) at temperatures rangingfrom about 100° C. to about 250° C., and, in some embodiments from about100° C. to about 225° C., and in some embodiments, from about 110° C. toabout 225° C. (e.g., 100° C., 125° C., 150° C., 175° C., or 200° C.).

The present invention may be better understood by reference to thefollowing example.

Test Procedures Vibration Testing at 23° and 125° C.

A vibration test was performed in accordance with IEC 68-2-6. Moreparticularly, the product was initially attached onto a printed circuitboard by Sn96.5-576 solder paste (EFD, Inc., U.S.A., 85.4-88.3% byweight of tin, 2.5-2.9% by weight of silver, 0.4-0.5% by weight ofcopper and rest of organic rosin and organic solvents). Next, the boardwas mechanically mounted onto a vibration table and the parts weresubjected to the entire frequency range of 10 Hz to 2.000 Hz and thenreturned to 10 Hz and reversed in 20 minutes. This cycle was performed12 times in each of orthogonal directions (a total of 36 times) so thatmotion was applied for a total period of approximately 12 hours. Thevibration amplitude was 3.0 mm from 10 Hz to the higher cross-overfrequency and then 20 g acceleration to 2.000 Hz.

The testing at 23° C.+2° C. was carried out using Derritron VP85/TW6000equipment. The testing at 125° C.+5° C. was carried out using LDS V850equipment and high temperature oven (Kittec).

Equivalent Series Resistance (ESR)

Equivalence series resistance may be measured using a Keithley 3330Precision LCZ meter with Kelvin Leads 2.2 volt DC bias and a 0.5 voltpeak to peak sinusoidal signal. The operating frequency was 100 kHz andthe temperature was 23° C.±2° C.

Capacitance

The capacitance was measured using a Keithley 3330 Precision LCZ meterwith Kelvin Leads with 2.2 volt DC bias and a 0.5 volt peak to peaksinusoidal signal. The operating frequency was 120 Hz and thetemperature was 23° C.±2° C.

Leakage Current:

Leakage current (“DCL”) was measured using a leakage test set thatmeasures leakage current at a temperature of 25° C. and at the ratedvoltage after a minimum of 60 seconds.

EXAMPLE

A tantalum anode (4.80 mm×5.25 mm×2.60 mm) was anodized at 118V in aliquid electrolyte to 47 μF. A conductive coating was then formed bydipping the entire anode into an aqueous solution of manganese(II)nitrate with different specific gravities and then decomposition at 250°C. The part was then coated with graphite and silver. A copper-basedleadframe material was used to finish the assembly process. A singlecathode connective member was attached to the lower surface of thecapacitor element using a silver adhesive. The tantalum wire of thecapacitor element was then laser welded to an anode connective member.The housing had gold plated solder pads on the bottom inside part ofceramic housing. To increase the degree of surface area available forsoldering to a circuit board, four (4) external copper terminations(length of 13.00 mm, a width of 2.00 mm and a thickness of 0.1 mm) wereattached as described and shown herein using Ag72 solder (71.0-73.0% byweight of silver and 27.0-29.0% by weight of copper) to the each goldplated solder pad on the housing.

The anode and cathode connective members of the leadframe were thenglued to a gold cathode termination and welded to a gold anodetermination located inside a ceramic housing having a length of 11.00mm, a width of 12.00 mm, and a thickness of 5.40 mm. The adhesiveemployed for the connections was a silver paste (EPO-Tek E3035) and theadhesive was applied only between the leadframe portions and gold platedsolder pads. After drying at 150° C. for 2 hours, a polymeric restraintmaterial (Dow Corning® 736 heat resistant sealant) was applied over thetop of the anode and cathode portions of the capacitor element and waspolymerized at 23° C. for 24 hours and after that was dried at 165° C.for 1.5 hours. After that, a Kovar® lid was placed over the top of thecontainer. The resulting assembly was placed into a welding chamber andpurged with nitrogen gas for 120 minutes before seam welding between theseal ring and the lid was. Forty (40) parts were made in this manner andthen tested for electrical performance (i.e., leakage current, ESR, andcapacitance after aging). The median of measurements conducted at 23° C.and at 125° C. after vibration testing are set forth below.

ESR Cap Conditions DCL [μA] [mOhm] [μF] Before Testing 1.9 54.4 116.8After Vibration @ 23° C. 2.1 54.9 116.3 After Vibration @ 125° C. 2.255.7 116.2

These and other modifications and variations of the present inventionmay be practiced by those of ordinary skill in the art, withoutdeparting from the spirit and scope of the present invention. Inaddition, it should be understood that aspects of the variousembodiments may be interchanged both in whole or in part. Furthermore,those of ordinary skill in the art will appreciate that the foregoingdescription is by way of example only, and is not intended to limit theinvention so further described in such appended claims.

What is claimed is:
 1. A capacitor assembly comprising: a capacitorelement comprising an anode formed from an anodically oxidized, sinteredporous body and a solid electrolyte coating the anode; a housing thatdefines an interior cavity within which the capacitor element ispositioned and hermetically sealed, wherein the housing contains asurface having a dimension in a longitudinal direction and a dimensionin a transverse direction, the surface further defining an outerperiphery; an anode termination that is in electrical connection withthe anode body, the anode termination containing an external anodetermination portion that is located adjacent to the surface of thehousing; and a cathode termination that is in electrical connection withthe solid electrolyte, the cathode termination containing an externalcathode termination portion that is located adjacent to the surface ofthe housing; wherein the external anode termination portion, theexternal cathode termination portion, or both extend outwardly beyondthe outer periphery of the housing surface in the transverse directionby a certain distance.
 2. The capacitor assembly of claim 1, wherein theexternal anode termination portion, the external cathode terminationportion, or both have at least one side that extends outwardly beyondthe outer periphery of the housing surface in the transverse directionby a certain distance, further wherein the side of the external anodetermination portion, the side of the external cathode terminationportion, or both are folded at the outer periphery, wherein the side isadjacent to a wall of the housing and perpendicular to the housingsurface.
 3. The capacitor assembly of claim 1, wherein the externalanode termination portion, the external cathode termination portion, orboth are provided in a plane that is generally parallel to the housingsurface.
 4. The capacitor assembly of claim 1, wherein the externalanode termination portion extends beyond the outer periphery of thehousing surface by a first distance in the transverse direction.
 5. Thecapacitor assembly of claim 4, wherein the ratio of the first distanceto the dimension of the housing surface in the transverse direction isfrom about 0.05 to about 3.0, and preferably from about 0.10 to about2.5.
 6. The capacitor assembly of claim 4, wherein the first distance isgreater than the dimension of the housing in the transverse direction.7. The capacitor assembly of claim 4, wherein the first distance is fromabout 0.5 to about 40 millimeters and the dimension of the housingsurface in the transverse direction is from about 2 to about 30millimeters.
 8. The capacitor assembly of claim 4, wherein each side ofthe external anode termination portion extends outwardly beyond theperimeter of the housing surface.
 9. The capacitor assembly of claim 1,wherein the external cathode termination portion extends beyond theouter periphery of the housing surface by a second distance in thetransverse direction.
 10. The capacitor assembly of claim 9, wherein theratio of the second distance to the dimension of the housing surface inthe transverse direction is from about 0.05 to about 3.0, and preferablyfrom about 0.10 to about 2.5.
 11. The capacitor assembly of claim 9,wherein the second distance is greater than the dimension of the housingin the transverse direction.
 12. The capacitor assembly of claim 9,wherein the second distance is from about 0.5 to about 40 millimetersand the dimension of the housing surface in the transverse direction isfrom about 2 to about 30 millimeters.
 13. The capacitor assembly ofclaim 9, wherein each side of the external cathode termination portionextends outwardly beyond the perimeter of the housing surface.
 14. Thecapacitor assembly of claim 1, wherein both the external anodetermination portion and the external cathode termination portion extendoutwardly beyond the outer periphery.
 15. The capacitor assembly ofclaim 1, wherein the external cathode termination portion, the externalanode termination portion, or both are discontinuous across thetransverse dimension of the housing surface.
 16. The capacitor assemblyof claim 1, wherein the porous body is formed from tantalum or niobiumoxide powder.
 17. The capacitor assembly of claim 1, wherein theinterior cavity has a gaseous atmosphere that contains an inert gas. 18.The capacitor assembly of claim 17, wherein inert gases constitute fromabout 50 wt. % to 100 wt. % of the gaseous atmosphere.
 19. The capacitorassembly of claim 1, wherein the housing is formed from a metal,plastic, ceramic, or a combination thereof.
 20. The capacitor assemblyof claim 1, further comprising a lead that extends in the longitudinaldirection from the porous body of the anode, wherein the lead ispositioned within the interior cavity of the housing.
 21. The capacitorassembly of claim 20, further comprising a connective member thatcontains a first portion that is positioned generally perpendicular tothe longitudinal direction of the anode lead and connected thereto. 22.The capacitor assembly of claim 21, wherein the connective memberfurther contains a second portion that is generally parallel to thelongitudinal direction in which the anode lead extends.
 23. Thecapacitor assembly of claim 22, wherein the second portion is positionedwithin the housing and is electrically connected to the external anodetermination portion.